At the “Year End Seminar of OLED/Display” held at COEX in Seoul, Korea, on December 7, Kim, Seok-Soon, CEO of Unijet said that ink-jet printing technology can implement over 550 RGB ppi and ink-jet printing can be applied to small and medium-sized OLED process as well.
The currently mass-produced QHD resolution of 5.5-inch mobile device is 550 ppi but it is actually 400 ppi with pentile structure. Moreover the ink-jet printing technology for RGB pixels is currently in the range of 150 to 200 ppi which can achieve 8K resolution on over 55inch OLED, yet inapplicable to the small and medium-sized OLED process. As Kim announced, if the ink-jet printing technology is applicable, implementing 550 ppi in the small and medium-sized OLED process, beyond QHD resolution in 5.5 inches, it is possible to implement UHD resolution in pentile structure.
<ppi by size and resolution>
Kim said, “In 2012, single droplet measurement technology showed 2.5% or less of volume accuracy, which was, however, insufficient for RGB printing. In 2017, the laser droplet measurement technology enabled the discharge volume control less than 0.1 μm and the real-time internal pressure control reduced the volume accuracy by less than 0.1%.” Kim added that it is possible to form over 550 RGB ppi regardless of the pixel structure.
Lastly, Kim noted that the solvent purity for OLED RGB pixel is very important; “Inkjet printer can be commercialized only if ink materials are fully developed first to satisfy panel makers. He expected that it will be applied to the mass production line in earnest since 2020. ”